Column spring switch



June 20, 1950 5. L. CLARK mu. 2,512,306

I COLUMN SPRING SWITCH I Filed NOV. '7, 1947 Inventors:

David L.Clar-k, James F. Young,

heir Attorney Patented June 2Q, 1950 2,512,309 comm: SPRING swrrcn David L. Clark and James F. Young, Bridgeport, Conn, asslgnors to General Electric Company, a corporation of New York Application November I, 1947, Serial No. 784,718

3 Claims. 1 This invention relates to snap action switches and more particularly to snap action switches of the column spring type, that is switches having an elongated resilient movable element of spring material restrained at both ends and under axial compression.

For satisfactory operation, it is desirable that switches of the column spring type have several characteristics. be constructed to provide a high contact pressure and tomaintain this pressure during the operation of the switch from one extreme position to another. It is further desirable to compensate automatically for wear of the contacts so that substantial contact pressure will be maintained throughout the life of the switch. Finally, to insure consistent operation of the switch, it is desirable to minimize. the effect of changes in temperature and humidity on the operation of the switch. By this invention, all the above desirable features are incorporated in a simple and inexpensive column spring switch.

Accordingly, it is an objectof this invention to provide a column spring switch including an improved arrangement for maintaining a high contact pressure.

It is another object of this invention to provide a column spring switch including an improved arrangement for maintaining end compression.

It is a further object of this invention to provide a column spring switch including an element for providing proper end compression and for automatically adjusting for wear of the contacts.

It is still another object of this invention to provide a column spring switch wherein the eflect of changes in temperature and humidity upon the operation of the switch is minimized.

Further objects and advantages of this invention will become apparent as the following description proceeds and the features of novelty which characterize this invention will be pointed out with particularity in the claims annexed to and forming part of this specification.

For a better understanding of this invention, reference may be had to the accompanying drawing in'which Fig. 1 is a sectional elevation view of a column'spring switch; Fig. 2 is a plan view taken along the line 22 of Fig. 1; Fig. 3 is a sectional elevation view taken along the line 3-3 of Fig. 1; Fig. 4 is an enlarged view of a portion of the switch shown in Fig. 1; and Fig. 5. is a perspective view showing the switch disassembled.

Referring now to Figs. 1 and 2, the switch includes a housing I of suitable electrical insulating material. The housing is composed of two 55 to the lower part 2 of the housing and is arranged- For example, the switch should a complementary parts 2 and 3 within which the switch mechanism is enclosed. The parts 2 and" 3 are held in assembled relationship by bolts. 4 and 5 or other fastening devices which pass through openings 6 and l in the upper housing part 3 and into engagement with threaded openings 8 and 9 in the lower housing part 2.

The upper and lower parts of the housing are provided with complementary recesses which in the assembled position cooperate to form a chamber Ill for receiving an operating portion of the switch mechanism. The switch mechanism includes a resilient frame member ll having an elongated aperture l2 extending longitudinally v thereof. In the form of the invention illustrated,

a resilient switch arm I3 is formed integral with the [frame member II and extends from a base portion ll of the frame member longitudinally of the aperture l2. In this form, the switch arm I3 is struck from the same strip of metal used to form the frame member II and extends substantially the entire length of the aperture l2 to bridge this aperture. It will be understood, however, that. if desired, the switch arm may be made from a separate strip and secured to the frame member II in position to bridge the aperture l2 longitudinally. If the switch arm is made as a separate strip, a material having the same characteristics as the material of the frame member is employed so as to minimize the effect of changes in temperature and humidity on the operation of the switch.

As shown more clearly in Fig. 5, the portions i5 and ii of the frame member which extend along the sides of the aperture l2 are positioned to be held between the lower part 2 and the upper part 3 of the housing l. The portions l5 and I6 rest respectively on ledges l1 and I8 formed in the lower part 2 of the housing, and the lower surface I! of the upper part 3 of the housing is pressed against the portions l5 and It by the bolts 4 and 5 in the assembled position of the switch. The .base portion ll of the frame member includes an opening 20 through which the .bolt 4 passes in the assembled position of the switch. The base portion l4 projects beyond the housing I and includes an opening 2l for receiving a suitable electrical lead.

Referring again to Figs. 1 and 2, an electrical contact 22 is secured to the switch arm l3. Adjacent this contact and in position to be selectively engaged thereby in the extreme positions of the switch-are two stationary terminals or contacts 23 and 24. The terminal 23 is secured to receive any suitable electrical lead connected to the external portion 26 of the terminal 23. The terminal 24 is similarly arranged on the upper part 3 of the housing. The switch arm I3 and the frame member I I with which it is integral are made of a, suitable current conducting material, such as beryllium copper, so as to provide a circuit from a lead secured to the base portion I4 at opening 2I selectively to either the terminal 23 or the terminal 24. The switch arm is adapted to move between one extreme position shown by solid lines in Fig. 1 wherein the contact 22 is in engagementwith the terminal 24 and a. second extreme position, shown by dotted lines in Fig. 1, wherein the contact 22 ism engagement with the terminal 23.

A resilient strip or member 26 is secured to the frame member II adjacent the free end of the switch arm I3 to provide an end compression for bowing the switch arm. The strip 26 is secured to the frame member by a bolt and nut 21 and 26 or by other suitable fastening devices. The strip 26 includes a U-shaped portion 23, and the end 36 of the strip extends into the aperture I2 in position to engage the free end of the switch arm I3. Since the switch arm I3 is substantially the same length as the aperture I2 the insertion of the resilient strip 26 between the end of the aperture and the end of the switch arm automatically effects a minimum end compression on the switch arm l3 and a minimum contact pressure dependent on the thickness of the end 36 of the strip 26. A portion 3I of the frame member II which forms one end of the aperture I2 provides a fixed abutment for limiting the movement of the resilient strip 26 and thereby prevents the strip 26 from moving at any time sufliciently far that contact pressure would be inadequate. When the switch arm is in either of its extreme positions, the end of the strip 26 moves to the left of the abutment 3I, as shown in Figs. 1 and 4, under its own natural resilience to maintain proper contact pressure and to provide a follow-up for wear of the contacts.

In order to move the switch from one extreme position to another, an actuator 32 of suitable electrical insulating material is provided. The actuator 32 is guided within the housing I by aligned openings 33 and 34 which are provided respectively in the upper part 3 and the lower part 2 of the housing. The actuator extends -through an elongated opening 35 in the switch arm I3 and is arranged to engage the sides of this opening. As shown most clearly in Fig. 3, the actuator 32 includes two recesses 36 and 31. The portions of the switch arm along the sides of the elongated opening .35 extend into these recesses 36 and 31 to prevent relative motion between the actuator 32 and the switch arm I3. In assembling the switch, the frame member II is turned at a 90 degree angle to the position shown in the drawing and the end of the actuator 32 is extended into the elongated opening 35, the length of the elongated opening exceeding the width of the actuator. The frame member is moved upwardly until the opening 35 is aligned with the recesses 36 and 31. The frame member is then turned to the position shown in the drawings. The portions of the switch arm ad-- jacent the sides of the opening 35 pass into the recesses 36, 31 in the actuator 32 to prevent disengagement of the actuator-.32 from the switch arm in the assembled position of the switch. The switch is biased to the position shown in Fig. 1 by a compression spring 33. One end of this spring presses against the housing I and the other end p against the top of the actuator 32. If desired, the biasing spring 38 may be omitted so that the switch will remain in either the solid line position or the dotted line position.

In order to provide for longitudinal movement of the free end of the switch arm I3 and to substantially prevent movement in a direction perpendicular to the plane of the switch arm the housing I is formed to provide a guide portion 36. As shown most clearly in Fig. 5, the lower part 2 of the housing includes a laterally extending ridge 46. The upper surface of the ridge 46 is slightly below the plane of the ledges II and I3 so that when the portions 2 and 3 of the housing are assembled the guide portion 33 is formed between the upper surface of the ridge 46 and the lower surface of part 3 of the housing. Referring again to Fig. 1, it can be seen that the free end of the switch arm I3 is slidably received within the guide portion 36 and is free to movelongitudinally within the confines of the guide portion.

The operation of the switch is as follows. The switch normally assumes the position shown in Fig. 1 in which the contact 22 is in engagement with terminal 24 and a circuit is completed from the projecting base portion I4 of the frame member through the switch arm I3 to the terminal 24. The switch assumes this position whenever the actuator 32 is released since the compression spring 33 .under such conditions moves the actuator 32 upwardly to snap the switch arm I3 over center to the position shown. When it is desired to operate the switch to the position shown by the dotted lines in Fig. 1, the actuator is pressed downwardly. As the actuator 32 is moved downwardly, the switch arm I3 exerts a greater force against the end 36 of the resilient strip 26 moving it to the position shown by the dotted lines in Fig. 4. When the end 36 of the resilient strip reaches the position shown by the dotted lines it comes into engagement with the stationary abutment 3i and further movementto the right is prevented. This limit of longitudinal movement of the free end of the switch arm I3 is reached before the switch arm has reached the intermediate position from which it snaps over center. Accordingly, as the downward movement of the actuator 32 is continued, relaxation of the contact pressure between contact 22 and terminal 24 is prevented. In fact, the contact pressure increases, as explained hereinafter, so that this pressure at the time the switch arm I3 snaps over center exceeds the contact pressure in the extreme positions of the switch arm shown by the solid lines and by the dotted lines in Fig. 1. As the downward movement of the actuator 32 continues, the switch arm ultimately moves over center and immediately snaps to the position shown by the dotted lines in Fig. 1. In this position, the contact 22 is in engagement with terminal 23 and a circuit is completed from the projecting base portion I4 of the frame member II through the switch arm I3 to the terminal 23. When the actuator is released, it moves upwardly under the influence of the compression spring 36 and the switch arm I3 ultimately snaps ove center to the position shown by the solid lines.

The eflective bowing-length of the switch arm I3 is included between the points 4| and 42. It will be noted that the contact 22 is arranged about one-fourth of the distance from one end ll of the effective length of the switcharm and the actuator engages the switch arm at a point approximately one-fourth of the distance from the opposite end 42 from the effective length of the switch arm. The arrangement of the actuator and the contact in these positions assists in maintaining [adequate contact pressure during the H movement of the switch from one extreme position to the other. It can be seen that as the actuator is pressed downwardly, there is a tendency to flatten the righthand end of the switch arm. Since the longitudinal movement of the free end of the switch arm is limited by the resilient member 26 which extends into the aperture i2 and engages the stationary abutment 9|, the extreme high point of the bowed switch arm gradually shifts toward the left in the direction of the contact 22. This shifting of the extreme point of the bowed portion toward the contact tends to increase the contact pressure and assist in maintaining adequate contact pressure.

While the specific form of this invention has been shown and describedfit is not desired to limit the invention to the particular construction shown and itis intended by the app nded claims to cover all modifications within the spirit and scope of this invention.

What we claim as new and desire to secure by Letters Patent of the United States, is:

1. A switch comprising a frame member havin a longitudinal aperture therein, an elongated resilient switch arm secured at one end to said frame member and extending substantially the full length of said aperture, and a resilient strip secured to said frame member and bearing against the free end of said switch arm for maintaining said switch arm in a bowed condition, said resilient strip extending into said aperture between the free end of said switch arm and an end of said aperture whereby the thickness of said strip determines the minimum end com-' pression on said switch arm.

2. A switch comprising a housing of electrical insulating material, a metallic frame member clamped within said housing in fixed position at one end thereof, said frame member having an elongated aperture therein, an elongated resilient switch arm having one end integral with said frame member and longitudinally bridging said aperture, said housing including a guide slot for slidably receiving the free end of said arm to permit only longitudinal motion of said free end, 1

end walls of said slot cooperating with the fixed securement portion of said frame to establish per- 55 manent fiexure points for said arm, a resilient member secured to said frame member, said resilient member extending into said aperture and bearing against the free end of said switch arm for maintaining said arm in a bowed condition whereby said switch arm selectively occupies one of two extreme positions, said frame member ineluding a stationary abutment for limiting the movement of said resilient member, said housing including a pair of aligned openings, an actuator slidably mounted in said aligned openings and engaging said switch arm for moving said arm over center, and a spring for biasing said actuator to maintainsaid switch normally in one extreme position.

3. In a column spring snap switch, the combination of a metallic frame having an elongated aperture therein, a switch arm of thin, springf able material fixedly secured by one end to said frame and extending longitudinally within said aperture for substantially the full length thereof, a housing secured to said frame at one end thereof, said housing having wall means defining a slot slidably accommodating said switch arm adjacent the free end portion thereof and holding said end portion substantially in the plane of the frame, said switch arm extending beyond said housing wall means, spring means secured by one end to said frame and penetrating said aperture to bear against the end wall of said switch arm to establish and maintain the portion thereof between the fixed end and the wall means in bowed condition, the frame wall defining an end of said aperture constituting an abutment in the plane of said switch arm end portion for limiting the movement of said spring means and means slidably carried by said housing and engaging said switch'arm intermediate the ends thereof for moving said arm over center to an op positely bowed position.

' DAVID L. CLARK.

JAMES EYOUNG.

' REFERENCES CITED The following references are of record in the file of this patent: I

UNITED STATES PATENTS 

